JPH0264586A - Developing device - Google Patents

Abstract

PURPOSE:To allow a developer carrier to bear a moderate quantity of developer with a well-balanced distribution in the lengthwise direction by sectionalizing the space between the developer carrier and a developer agitating member with a partition different in height in the lengthwise direction and placing the developer carrying pole of a magnetic field generating means so that it is upflow the partition in the development movement direction in any position in the lengthwise direction. CONSTITUTION:A hopper 9 of a developing device 2 is opened in a developing vessel, and a developer supply means 10 is arranged in the vicinity of this aperture part and is rotated in accordance with the signal of a developer quantity detecting element 11 attached to the end face of the device 2, and toner T supplied from the hopper 9 is agitated and carried in the lengthwise direction by an agitating and carrying means 6. A partition 7 between a developing sleeve 4 of the device 2 and the carrying means 6 has the height linearly reduced from the toner supply side toward the depth and is so arranged that a maximum density position of the magnetic flux on the sleeve 4 of a carrying pole S2 of a magnetic toll 3 fixed in the sleeve 4 is placed under the lowest position C of the partition.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is utilized in the field of image forming technology such as electrophotographic copying machines and information recording devices, and is particularly applicable to latent images formed on electrostatic latent image carriers. The present invention relates to a dry developing device for converting an image into a visible image.

[Prior Art] Recently, with the increasing need for color copies, inexpensive and compact monochrome copying machines have been increasing in number. Since a plurality of developing devices are provided inside the device, each developing device is downsized and its developer storage capacity is also reduced, so a developer supply container (hereinafter referred to as a hopper) is often provided separately. In this case, it would be ideal for the developer to be supplied from the hopper to the developing device uniformly over the entire axial direction of the developer carrier, but since there is not enough space above the developing device, The device is stretched longer than the length of the latent image carrier, and a hopper is provided on the stretched portion, and developer is supplied from the hopper to the developing device.

However, in the case of the above configuration, the supply of developer from the developer supply side of the developer agitation conveyance means to the other side (back side) cannot keep up, resulting in an image not appearing or an excessive supply of developer. The developer may aggregate on the back side of the developing device, resulting in abnormal images. Furthermore, since there is a difference in particle size distribution, physical properties, etc. between the supplied developer and the well-stirred developer, there is a difference in the development characteristics between the developer supply side and the back side, which affects the homogeneity of the image. To solve this problem, a partition wall is provided between the developer carrier and the agitation conveyance means, and the partition wall is gradually extended from the developer supply side to the opposite side (downstream in the direction of conveyance by the agitation conveyance means). I was trying to keep it low. FIG. 4 is a schematic cross-sectional view showing a conventional developing device, in which a magnet 3 is fixed inside so as to face an electrophotographic photosensitive drum 1 as an image carrier, and a rotating developer carrier. A non-magnetic developing sleeve 4 is provided.

To explain with reference to FIG. 2, a hopper 9 containing toner T to be replenished is provided at the upper end of one longitudinal end of the developer storage container 2, and the hopper 9 is located inside the developing device 2. The developer supply member 1 is opened in the vicinity of the opening.
0 is set. Further, a developer amount detection element 11 is attached to the end face of the developing device 2 on the side where the hopper 9 is provided, and the supply member 10 rotates in response to a signal from the element 11, and toner is supplied from the hopper 9. The supplied toner is conveyed in the longitudinal direction by an agitation conveyance means (such as a screw fin) 6 while being agitated with the magnetic carrier particles in the container 2, and is conveyed between the developing sleeve 4 and the agitation conveyance means 6 (
After passing over the partition wall 7 (which is linearly lowered from the developer supply side toward the downstream direction in the transport direction by the agitation transport means),
It is supplied and carried on the developing sleeve.

Furthermore, a magnetic pole N is provided on the surface of the developing sleeve 4.

The developer is coated in a thin layer by the magnetic force of the magnet roller 3 whose positions are fixed, the action of the magnetic blade 5, and the rotation of the developing sleeve 4 in the direction of arrow A in the figure. The electrostatic latent image formed on the photosensitive drum 1 is developed by the toner of the developer.

[Problems to be Solved by the Invention] However, when an image reproduction durability test was actually conducted using the developing device having the above configuration, the image density gradually decreased toward the back side. Furthermore, the amount of toner on the sleeve at the back of the developing device became excessive, causing the toner to aggregate and produce an abnormal image.

Furthermore, when a toner having a small average particle diameter (4 to 9 μm in volume average diameter) was used as a developer with the intention of improving image quality, the toner agglomerated further and caused a large decrease in density.

After examining these phenomena, we found the following.

l) The reason why the density on the back side gradually decreased is because the amount of toner on the sleeve on the back side in the developing device became too large, and the toner agglomerated and the amount of charge of the toner decreased.

it) As mentioned above, the reason for the excessive amount of toner on the back side is the developer transport pole S2 of the magnet in the developing sleeve 4.
(The developer that has gone over the partition wall 7 is attracted to the sleeve and transported by the magnetic force of this pole.) Because the pole is located above the partition wall at the lower back side of the partition wall 7, the amount of toner taken into the developing sleeve is large. It is because of what happened.

As is clear from the above, the problem with the above-mentioned conventional developing device is that it is located between the developing sleeve and the developer stirring and conveying member, and is gradually lowered from the developer supply side to the other side (back side). This is due to the fact that the transport pole of the magnet in the developing sleeve is located at the top only on the back side with respect to the partition wall.

[Means for Solving the Problems] The present invention provides a developer carrier rotatable in a predetermined direction, a fixed magnetic field generating means disposed inside the developer carrier, and a developer accommodated therein. In the developing device, the developing device includes a container in which the developer is stirred, and a developer stirring member disposed close to the developer carrying member within the container. In contrast, the developer transport poles of the magnetic field generating means are positioned upstream of the partition walls in the developer movement direction at all positions in the longitudinal direction.

[Embodiment] FIGS. 1 and 2 show a first embodiment of the present invention. As mentioned above, the hopper 9 in FIG. 2 opens into the developer container 2, and the developer supply member 10 is provided near the opening, and the developer amount detection element 11 is attached to the end face of the developing device 2. The toner (T) is supplied from the hopper 9 and is agitated and conveyed in the longitudinal direction by the agitation conveyance means 6 (screw fins, etc.).

As shown in FIG. 2, the partition wall 7 between the developing sleeve 4 and the agitation conveyance means 6 is linearly lowered from the toner supply side toward the back (downstream in the developer conveyance direction by the agitation conveyance means 6). In addition, the transport pole S2 of the magnet roller 3 fixed in the developing sleeve 4 has a maximum magnetic flux density position on the sleeve below the lowest position C of the partition wall 7 (developer transport by the sleeve). It is arranged so that it is located on the upstream side in the direction.

The developer (including toner and magnetic carrier) stirred and transported in the longitudinal direction overcomes the partition wall 7 and is carried on the developing sleeve 4, but unlike the conventional example, the transport pole S2 is located at the top of the partition wall 7 only on the back side. Therefore, a uniform amount of toner is carried over the length of the developing sleeve.

When an image output durability test was conducted using the developing device of this example, it was found that good images were obtained over a long period of time without the image density on the back side decreasing like in the conventional example, and the amount of toner in the developing device was It was also well balanced in the longitudinal direction.

In addition, the toner average particle size is small (volume average 4 to 9 μm).
Similar results were obtained when using m), and high quality images were obtained for a long period of time.

FIG. 3 shows a second embodiment.

In the second embodiment, from near the center in the longitudinal direction of the developing device 2,
Toner is supplied from a hopper. The supplied toner is agitated and conveyed toward both ends by an agitation conveyance means 6 (such as a screw with a different helical direction from the center). The partition wall 7 is linearly lowered from the center to both ends. At this time, similarly to the first embodiment shown in FIG. 1, the conveying pole S of the magnet roll is arranged so that the maximum magnetic flux density position on the sleeve is located below the lowest position C of the partition wall 7. , the same effects as the first embodiment can be obtained.

[Effects of the Invention] As explained above, according to the developing device of the present invention,
Since an appropriate amount of developer is carried on the developer carrier in a well-balanced manner in the longitudinal direction, it is possible to always provide a good visible image.

[Brief explanation of the drawing]

1 and 2 are schematic configuration diagrams of one embodiment of the present invention, FIG. 3 is a schematic diagram of another embodiment of the present invention, and FIG. 4 is a schematic diagram of a conventional device. 2 is a container, 3 is a magnet, 4 is a sleeve, 6 is an agitation conveyance member, and 7 is a partition wall.

Claims (2)

[Claims] (1) A developer carrier rotatable in a predetermined direction, a fixed magnetic field generating means disposed inside the developer carrier, a container containing a developer therein, and the developer in the container. A developing device including a developer stirring member disposed close to a developer carrying member, wherein the developer carrying member and the developer stirring member are partitioned by partition walls having different heights in the longitudinal direction. Further, a developing device characterized in that the developer transport pole of the magnetic field generating means is located upstream of the partition wall in the developer movement direction at all positions in the longitudinal direction. (2) The developing device according to claim (1), wherein the toner used as the developer has a volume average diameter of 4 to 9 micrometers.